The vertebrae of the human spine are arranged in a column with one vertebra on top of the next. Between each vertebra exists an intervertebral disc that transmits force between adjacent vertebrae and provides a cushion between the adjacent vertebrae.
Sometimes, back pain is caused by degeneration or other deformity of the intervertebral disc (“diseased disc”). Conventionally, surgeons treat diseased discs by surgically removing the diseased disc and inserting an implant in the space vacated by the diseased disc, which implant may be bone or other biocompatible implants. The adjacent vertebrae are then immobilized relative to one another. Eventually, the adjacent vertebrae grow into one solid piece of bone.
For example, a conventional method to fuse vertebrae together includes a bone graft and a plate to stabilize the device. The current process includes inserting a bone graft and fusing the adjacent vertebrae together. Traditionally, inserting a bone graft involves distracting the disc space and manually keeping the vertebral bodies separated. The bone graft or implant is located and, once the implant is placed, the surgeon releases the adjacent vertebrae allowing them to squeeze the implant and hold it in place.
To immobilize the vertebrae with the implant in place, the surgeon next applies a plate over the adjacent vertebrae. The plate may have a central viewing window and one or more screw holes. Typically, four bone screws would be screwed into the vertebrae using the screw holes to anchor the cervical plate to the vertebrae and immobilize the vertebrae with respect to one another.
Immobilizing the superior and inferior vertebrae with a bone graft in the intervertebral disc space prompts fusion of the superior and inferior vertebrae into one solid bone. As can be appreciated, the superior and inferior vertebrae are distracted to allow sufficient space for the surgeon to implant and orient the implant. This tends to increase the trauma to the surrounding tissue. Thus, it would be desirous to develop a compact fusion device that is expandable such that it can be inserted in a compact package allowing surgical site to be smaller, reducing the trauma to surrounding tissue.